Vitreous compositions based on Li3 PO4 and LiPO3 as network formers and network modifiers

ABSTRACT

Vitreous solid compositions at 25° C. are useful as solid state electrolytes and are comprised of either Li 3  PO 4  or LiPO 3  as a network former and/or network modifier.

This invention relates to vitreous compositions and their use as solidstate electrolytes.

Compositions which are solid at room temperature, are electricallyinsulative and ionically conductive can be used as solid stateelectrolytes. These electrolytes are desirable in cells in which aliquid electrolyte is disadvantageous. Examples of such cells areminiature cells which are stored for extended periods and where liquidelectrolytes are difficult to handle. Another example is in themanufacture of solid state microbatteries.

Although the solid state electrolytes exhibit lower specificconductivities than the liquid electrolytes, the solid stateelectrolytes can be used in devices and circuits which operate on lowcurrents.

Examples of solid state electrolytes are metallic salts and vitreoussolid compositions. Examples of metallic salt solid electrolytes includecompounds that conform to the formula: AgI-MCN-AgCN, wherein M ispotassium, rubidium, cesium or mixtures thereof.

Vitreous solid compositions, or glasses, are generally comprised of anetwork former, a network modifier and a network dopant. A networkformer provides a macromolecular network of irregular structure. Anetwork modifier is an ionic compound which becomes incorporated intothe macromolecular network of the network former. A network dopantprovides mobile cations to the network. Typically these glassprecursors, in powder form, are added together, heated sufficiently tofuse them together and then cooled to form the vitreous solid. Anexample of a vitreous solid composition employing a phosphorusoxide-sulfide network former corresponds to the formula:

    P.sub.4 O.sub.a S.sub.b,cLi.sub.2 S,dLi.sub.2 O,eX

wherein

X is a dopant selected from the group consisting of LiBr, LiCl, LiF,LiI, Li₂ CO₃, Li₂ SO₄, Li₂ SiO₃ and Li₄ SiO₄ ;

a is equal to (10-b) with b being greater than 0 and less than 10 withthe proviso however that when b is 6, a can be 3;

c and d are from 0 to about 4 with the proviso that when c and d areboth greater than 0 then d=4-c, and when c or d is 0 then d or c,respectively, is greater than 0; and

e is from 0 to about 7.

The network former is selected from P₄ O₉ S, P₄ O₈ S₂, P₄ O₇ S₃, P₄ O₆S₄, P₄ O₅ S₅, P₄ O₄ S₆, P₄ O₃ S₆, P₄ O₃ S₇, P₄ O₂ S₈ and P₄ OS₉, and isformed by mixing and heating P₂ O₅ with P₂ S₅. The network modifier isselected from Li₂ S and Li₂ O.

Although these electrolytes exhibit desirable conductivities, thevitreous solid is difficult to prepare from the mentioned compoundsbecause Li₂ O and P₂ O₅ are extremely hygroscopic. Therefore, the use ofsuch compounds is inhibited.

It would be desirable to have new vitreous solid compositions that couldbe prepared with easy to handle raw materials, and that would exhibitacceptable specific conductivities.

SUMMARY OF THE INVENTION

This invention is a vitreous solid composition at 25° C., comprising Li₃PO₄ or LiPO₃ as a network former and/or network modifier.

In another aspect, this invention is a vitreous solid composition at 25°C. which comprises the vitreous product formed under glass-formingconditions from phosphorus sulfide and either Li₃ PO₄ or LiPO₃ as anetwork former, Li₂ S as an optional network modifier, and a networkdopant selected from the group consisting of LiI, LiBr, LiCl, and LiF.

In yet another aspect, this invention is a mixture that corresponds tothe formula:

    xLi.sub.2 S, yP.sub.2 S.sub.5, (1-x-y)A, zLiX

wherein:

A is either Li₃ PO₄ or LiPO₃ ;

X is a halide, i.e. I, Br, Cl, or F;

x is a real number greater than or equal to 0 and less than or equal to0.68;

y is a real number greater than or equal to 0.15 and less than or equalto 0.33;

x+y is a real number greater than 0 and less than 1; and

z is a real number greater than or equal to 0.55 and less than or equalto 1.2.

In still yet another aspect, this invention is a vitreous solidcomposition at 25° C. formed under glass-forming conditions from theabove-mentioned precursor mixture.

In still yet another aspect, this invention is an electrochemical cellemploying an active anode material, an active cathode material and theabove-mentioned vitreous solid compositions as a solid stateelectrolyte.

In another aspect, this invention is a process for preparing a vitreoussolid film by sputtering a target composition comprised of theabove-mentioned precursor mixture.

In still yet another aspect, this invention is a microbattery that isless than 100 microns thick. The microbattery is comprised of asputtered metal film contact supported on a substrate, a sputtered filmcathode layer in contact with the metal film contact, a sputtered filmof the above mentioned vitreous solid composition over the cathode andcontact, and a vapor deposited anode layer deposited over theelectrolyte layer and a separate metal film contact.

Also, this invention is a process for preparing vitreous solidcompositions. The process comprises heating a mixture of powders of anetwork former, network modifier and network dopant to temperaturessufficient to fuse the mixture. The mixture is then cooled to 25° C.Either lithium metaphosphate or lithium orthophosphate is used as anetwork former and/or network modifier.

Further, this invention is a vitreous composition corresponding to theformula:

    xLi.sub.2 S, yP.sub.2 S.sub.5, (1-x-y)Li.sub.3 PO.sub.4, zLiX;

wherein:

X is a halide;

x is a real number greater than or equal to zero and less than or equalto 0.68;

y is a real number greater than or equal to 0.15 and less than or equalto 0.33;

z is a real number greater than or equal to 0.55 and less than or equalto 1.2; and wherein, either:

y is less than 0.2x+0.2, or

z is greater than 1.75(1-x+y).

In another aspect, this invention is a vitreous compositioncorresponding to the formula:

    xLi.sub.2 S, yP.sub.2 S.sub.5, (1-x-y)LiPO.sub.3, zLiX;

wherein:

X is a halide;

x is a real number greater than or equal to 0 and less than or equal to0.68;

y is a real number greater than or equal to 0.15 and less than or equalto 1.2; and wherein, either:

y is less than x-0.33, or

z is greater than 1.75(1-x+y).

Employing lithium orthophosphate, Li₃ PO₄, and lithium metaphosphate,LiPO₃, as sources of the network formers, and optional network modifier,in the vitreous solid compositions of this invention avoids thedisadvantages of using P₂ O₅ as the network former and Li₂ O as thenetwork modifier encountered in previous compositions. Further, the Li₃PO₄ and LiPO₃ can be employed as both the network former and networkmodifier, and can provide the sole source of oxygen to the network. Thecompositions have specific conductivities that enable them to be used aselectrolytes.

DETAILED DESCRIPTION OF THE INVENTION

A vitreous solid composition is one which is a glassy non-crystallinesolid. The compositions of this invention are vitreous solids at 25° C.

Lithium orthophosphate, Li₃ PO₄, or lithium metaphosphate, LiPO₃, areused as a network former and/or a network modifier. They can be used asboth the network former and network modifier, or with other formers andmodifiers. These compounds provide oxygen to the glass network.Preferably, they are the sole source of oxygen. Phosphorus sulfide canbe used as an additional network former. The amount of Li₃ PO₄ and LiPO₃employed can vary according to the amount of phosphorus sulfide andadditional network modifier employed.

Lithium orthophosphate is readily prepared by the reaction of H₃ PO₄ andLiOH and is readily commercially available.

Lithium metaphosphate is readily prepared by the reaction of HPO₃ andLiOH and is readily commercially available.

Phosphorus sulfide, P₂ S₅, is prepared by the reaction of phosphorus andsulfur and is readily commercially available.

Lithium sulfide, Li₂ S, can be used as an additional network modifieralong with the lithium orthophosphate and lithium metaphosphate. Lithiumsulfide is readily commercially available. Other modifiers can beemployed as well, such as lithium oxide, but lithium sulfide ispreferred. The amount of lithium sulfide employed can vary according tothe amount of phosphorus sulfide and lithium orthophosphate and lithiummetaphosphate employed.

The network dopants employed in this invention are lithium halides, i.e.lithium iodide, LiI; lithium bromide, LiBr; lithium chloride, LiCl; andlithium fluoride, LiF. The dopants are employed in an amount effectiveto enhance the conductivity of the composition.

The vitreous solid compositions of this invention are prepared underglass-forming conditions. Such conditions are those methods known forpreparing glasses or vitreous compositions. One such conventional methodis by fusing the precursors. For example, the compositions can beprepared by mixing the network former, network modifier and networkdopant precursors, in powder form, and then heating the powder mixtureat a temperature sufficient to melt the mixture to form a fusedcomposition. This fused composition is then cooled to yield the glass orvitreous composition. Specifically, the precursors can be blended in aninert atmosphere box whose atmosphere is preferably dry, for example,one that contains less than 10 ppm of water. The mixture can bepelletized and inserted into a tube that can withstand the fusiontemperatures and that is open at one end. The open end is stoppered andthe tube containing the pelletized glass precursors is removed from theinert atmosphere box. The tube is evacuated and the open end is sealedby melting and collapsing it in a flame. The evacuated sealed tube isthen heated to a temperature sufficient to fuse the mixture. Generally,above 950° C. is sufficient. The mixture is heated at this temperaturefor 15 minutes, and then the temperature is lowered somewhat, to about750° C., and then maintained for 15 minutes. The tube containing themolten solid electrolyte is then quenched in cold water to about 25° C.The silica tube containing the glassy solid electrolyte is then returnedto the inert atmosphere box, broken and the solid electrolyte isrecovered and ready for use in an electrochemical cell. These bulkvitreous compositions can exhibit specific conductivities of greaterthan about 0.75×10⁻⁴ S/cm².

In another method, the vitreous composition can be made in a sputteringprocess. In this process, a target is prepared from a compressed mixtureof the powdered precursors. The target is then placed in a vacuumchamber, and ionized gas, such as argon, is used to sputter a film ofthe vitreous composition from the target. These sputtered film vitreouscompositions can exhibit specific conductivities of greater than about1×10⁻⁶ S/cm².

The vitreous solid compositions of this invention are formed from aprecursor mixture that corresponds to the formula:

    xLi.sub.2 S, yP.sub.2 S.sub.5, (1-x-y)A, zLiX

wherein:

A is either Li₃ PO₄ or LiPO₃ ;

X is a halide, i.e., I, Br, Cl or F;

x is a real number greater than or equal to 0 and less than or equal to0.68;

y is a real number greater than or equal to 0.15 and less than or equalto 0.33;

x+y is a real number greater than 0, and less than 1; and

z is a real number greater than or equal to 0.55 and less than or equalto 1.2.

Preferred vitreous solid compositions of this invention are formed fromprecursor mixtures that correspond to the formulae:

a. 0.66 Li₂ S, 0.26 P₂ S₅, 0.08 Li₃ PO₄, 0.57 LiX;

b. 0.61 Li₂ S, 0.31 P₂ S₅, 0.08 Li₃ PO₄, 0.62 LiX;

c. 0.67 Li₂ S, 0.28 P₂ S₅, 0.05 Li₃ PO₄, 0.65 LiX;

d. 0.14 Li₂ S, 0.23 P₂ S₅, 0.63 Li₃ PO₄, 0.96 LiX;

e. 0.25 Li₂ S, 0.25 P₂ S₅, 0.50 Li₃ PO₄, 1.0 LiX;

f. 0 Li₂ S, 0.20 P₂ S₅, 0.8 Li₃ PO₄, 1.2 LiX;

g. 0.61 Li₂ S, 0.31 P₂ S₅, 0.08 LiPO₃, 0.62 LiX;

h. 0.57 Li₂ S, 0.29 P₂ S₅, 0.14 LiPO₃, 0.57 LiX;

i. 0.65 Li₂ S, 0.31 P₂ S₅, 0.04 LiPO₃, 0.58 LiX;

j. 0.50 Li₂ S, 0.17 P₂ S₅, 0.33 LiPO₃, 0.58 LiX;

wherein X is a halide, and preferably is either I or Br.

Other preferred compositions can correspond to the following formulae.Although these formulae will be described relative to the amounts of theprecursors used, it shall be understood that the formulae apply to theresulting glass or vitreous composition itself, regardless of the typesand amounts of precursors used. For lithium orthophosphate, Li₃ PO₄, thecompositions correspond to the formula:

    xLi.sub.2 S, yP.sub.2 S.sub.5, (1-x-y)Li.sub.3 PO.sub.4, zLiX;

wherein

X is a halide;

x is a real number greater than or equal to 0 and less than or equal to0.68;

y is a real number greater than or equal to 0.15 and less than or equalto 0.33;

z is a real number greater than or equal to 0.55, and less than or equalto 1.2; and wherein, either:

y is less than 0.2X+0.2, or

z is greater than 1.75(1-x+y).

For lithium metaphosphate, LiPO₃, the compositions correspond to theformula:

    xLi.sub.2 S, yP.sub.2 S.sub.5, (1-x-y)LiPO.sub.3, zLiX;

wherein

X is a halide;

x is a real number greater than or equal to 0 and less than or equal to0.68;

y is a real number greater than or equal to 0.15 and less than or equalto 0.33;

z is a real number greater than or equal to 0.55 and less than or equalto 1.2, and, wherein, either:

y is less than x-0.33, or

z is greater than 1.75(1-x+y).

The vitreous compositions of this invention are useful as electrolytesin electrochemical cells. The cells are comprised of an active anodematerial, an active cathode material and the electrolyte.

Suitable active anode materials include lithium, silver, sodium,potassium and rubidium. The materials can be used as alloys or puremetals. The anodes can be in foil or powder form. The preferred anode islithium metal and lithium alloys.

Suitable active cathode materials include TiS₂, FeS₂, Sb₂ S₃, MoS₃, TiS₂+MoS₃, organic charge transfer complexes with halogens, and MnO₂.Preferably, TiS₂ is employed as the active cathode material. TiS₂ can beprepared by reacting a titanium sponge with finely divided sulfur. It isalso commercially available, for example, from Degussa A. G., Frankfurt,W. Germany.

For electrochemical cells that employ the vitreous composition in bulkform, the cathode comprises the active cathode material, a conductiveagent and some of the vitreous composition to be employed as theelectrolyte. Suitable conductive agents include carbon, graphite, andmetal powders such as nickel. For microbatteries, preferably the cathodeis a sputtered film comprised solely of the active material.

One preferred type of microbattery that employs the vitreous solidcompositions as electrolytes uses a TiS₂ cathode and a lithium metalanode. These microbatteries are less than 100 microns, and preferablyless than 75 microns thick. To prepare these microbatteries, a metalliccontact is attached to a substrate by sputtering a film of the metal.The substrate can be any electrically insulative solid supportsubstance, such as a glass, plastic or resin. Any metal that isconductive and can be sputtered can be employed. Preferred examplesinclude platinum and chromium. A film of the TiS₂ is sputtered onto themetallic contact. Next, a layer of the vitreous solid composition isdeposited to cover both the TiS₂ film and a portion of the chromiumcontact. The vitreous composition is prepared by forming a targetcomprised of a compressed mixture of the powdered precursors, i.e.network former, network modifier and dopant, and then depositing a layerof the vitreous composition through a mask using a RF magnetronsputtering source. Preferably over this electrolyte layer is deposited aprotective layer. This protective layer protects the lithium anode fromreacting with the electrolyte. Any material that is relativelyunreactive toward the electrolyte and lithium and that is ionicallyconductive can be employed. A preferred example is LiI, or other networkdopant material. The lithium metal anode layer can then be depositedover the protective layer using vapor deposition techniques. Preferably,the microbattery is constructed in a dry room since the components arereactive to moisture. Advantageously, less than 5 ppm water is present.Preferably, the microbattery is encapsulated in a suitable encapsulantto isolate the microbattery from the atmosphere. Examples of suitableencapsulants include electrically insulative resins. A preferredencapsulant is FC-721, a fluoropolymer available from 3M Corp.

The Drawing depicts a preferred microbattery 1. The microbattery 1comprises a substrate 5 to which is attached chromium contacts 10 and12. TiS₂ cathode 15 is in contact with chromium contact 10. Vitreoussolid electrolyte 20 covers TiS₂ cathode 15 completely and edge 11 ofchromium contact 10. Protective layer 25 of LiI completely coversvitreous solid electrolyte 20. Li anode layer 30 partially coversprotective layer 25 and is in contact with chromium contact 12 tocomplete microbattery 1.

Preferred vitreous solid electrolytes for use in a microbattery have alow sulfur content. One preferred electrolyte composition is formed froma precursor mixture that corresponds to the formula:

    0 Li.sub.2 S, 0.20 P.sub.2 S.sub.5, 0.80 Li.sub.3 PO.sub.4, 1.2 LiI.

In other cases, it can be preferred that the electrolyte be completelyfree of sulfur. The microbatteries can exhibit an open circuit voltageof 2.5 V and show a discharge efficiency of about 90% to a 1.8 V cutoffat a current density of at least 8 microamps/cm². Thus, these batteriescan be used in micro-devices, such as memory back up in computer chips,and in sensors such as dissolved oxygen sensors that are used in themedical, biological and environmental industries.

The following examples illustrate the invention, but do not limit itsscope.

EXAMPLE 1

A vitreous composition is prepared using 0.66 mole of Li₂ S as a networkmodifier, 0.26 mole P₂ S₅ and 0.08 mole Li₃ PO₄ as network formers, and0.57 mole LiI as a network dopant. The components are in powder form,are mixed and sealed under vacuum in a fused silica tube. This mixtureis heated at 950° C. for fifteen minutes followed by 15 minutes heatingat 750° C. A fused composition results that is then cooled by rapidquenching to 25° C. to provide the vitreous composition. The compositionhas a specific conductivity of 5.9×10⁻⁴ S/cm at 25° C., and anactivation energy of 0.29 eV.

EXAMPLE 2

A vitreous composition is prepared using the same precursors andaccording to the method described in Example 1, except that 0.57 mole ofLiBr is employed as the network dopant rather than LiI. This compositionhas a conductivity of 2.4×10⁻⁴ S/cm at 25° C. and an activation energyof 0.36 eV.

EXAMPLE 3

A vitreous composition is prepared using 0.61 mole of Li₂ S as a networkmodifier, 0.31 mole of P₂ S₅ and 0.08 mole of Li₃ PO₄ as networkformers, and 0.62 mole of LiI as a network dopant. The components are inpowder form, are mixed and sealed under vacuum in a fused silica tube.This mixture is heated at 950° C. for 15 minutes followed by heating at750° C. for 15 minutes. This fused mixture is rapidly quenched to 25° C.A vitreous composition results that has a conductivity of 5.6×10⁻⁴ S/cmat 25° C. and an activation energy of 0.29 eV.

EXAMPLE 4

A vitreous composition is prepared using 0.61 mole Li₂ S as a networkmodifier, 0.31 mole of P₂ S₅ and 0.08 mole LiPO₃ as network formers, and0.62 mole of LiI as a network dopant. The composition is made accordingto the method described in Example 3, and the resulting composition hasa conductivity of 3.3×10⁻⁴ S/cm at 25° C. and an activation energy of0.34 eV.

EXAMPLE 5

A vitreous composition is prepared according to the method described inExample 3 using 0.57 mole of Li₂ S as a network modifier, 0.29 mole P₂S₅ and 0.14 mole LiPO₃ as network formers, and 0.57 mole of LiI as anetwork dopant. The composition has a conductivity of 2.3×10⁻⁴ S/cm at25° C. and an activation energy of 0.34 eV.

EXAMPLE 6

An electrochemical cell is prepared using a lithium foil anode, TiS₂ asthe active cathode material and the vitreous composition of Example 1 asthe electrolyte. The cell size has an outside diameter of 0.787 in. anda height of 0.061 inch. The cathode mix is prepared by mixing about 0.17gm of TiS₂ with about 0.11 gm of the vitreous composition of Example 1.The cathode has a diameter of about 0.63 inch and a discharge capacityof about 40 mAh. About 0.1 gm of the vitreous composition is employed asan electrolyte disc, and has a diameter of about 0.64 inch. Severalcells are discharged at 10K ohm, 15K ohm and 30K ohm to a cutoff voltageof 1.4 volts. The average performance at 10K ohm is 11.1 mAh dischargecapacity, representing an efficiency of 27.3% of theoretical input. Themidlife discharge voltage (MLV) is 1.97 volts. At 15K ohm, the averageperformance is 17.2 mAh discharge capacity, representing an efficiencyof 43%. The MLV is 1.94 volts. At 30K ohm, the average performance is34.4 mAh discharge capacity representing an efficiency of 85%. The MLVis 2.0 volts.

EXAMPLE 7

Electrochemical cells are prepared using the electrolyte and cathode mixof Example 6 and a Li powder anode rather than a Li foil anode. Severalcells are discharged at 7.5K ohm to a cutoff voltage of 1.4 volts. Theaverage performance is 28.3 mAh discharge capacity representing anefficiency of 70.7% of theoretical input. The MLV is 1.94 volts.

EXAMPLE 8

Electrochemical cells are prepared employing a Li foil anode, TiS₂active cathode material and the composition of Example 2 as theelectrolyte. The cathode is a mixture of about 0.17 gm of TiS₂ and about0.11 gms of the composition of Example 2. The cell size is the same asused in Example 6. The cathode has a diameter of about 0.64 inch and acapacity of about 40 mAh. About 0.09 gm of the composition of Example 2is used as the electrolyte. The electrolyte disc has a diameter of about0.64 inch. Several cells are discharged at 10K ohm, 15K ohm and 30K ohmto a cutoff voltage of 1.4 volts. At 10K ohm, the average performance ofthe cells is 6.2 mAh discharge capacity, representing an efficiency of15.5% of theoretical input. The MLV is 2.0 volts. At 15K ohm, theaverage performance is 10.5 mAh discharge capacity representing anefficiency of 26.2%. The MLV is 1.96 volts. At 30K ohm, the averageperformance is 25.6 mAh discharge capacity representing an efficiency of64%. The MLV is 1.94 volts.

EXAMPLE 9

Electrochemical cells are prepared employing the cathode mix andelectrolyte as in Example 8. The anode is Li powder. The cells aredischarged at 15K ohm to a cutoff voltage of 1.4 volts. The averageperformance is 27.3 mAh discharge capacity representing an efficiency of69%. The MLV is 1.96 volts.

EXAMPLE 10

Electrochemical cells are prepared using a Li foil anode, TiS₂ activecathode material and the composition of Example 4 as the electrolyte.The cathode mix is about 0.16 gm of TiS₂ and about 0.14 gm of theelectrolyte composition of Example 4. The cathode has a diameter ofabout 0.63 inch and a capacity of about 40 mAh. About 0.1 gm of thecomposition of Example 4 is used as the solid electrolyte disc and ithas a diameter of about 0.64 inch. The cells are discharged at 30K ohmto a cutoff voltage of 1.4 volts, and the average performance is 33.6mAh discharge capacity representing an efficiency of 84%. The MLV is2.05 volts.

EXAMPLE 11

Electrochemical cells are prepared employing a Li foil anode, TiS₂active cathode material and the composition of Example 5 as theelectrolyte. A cathode mix is prepared from about 0.18 gm of TiS₂ andabout 0.12 gm of the electrolyte composition of Example 5. The cathodehas a diameter of about 0.63 inch and a capacity of about 44 mAh. About0.11 gm of the composition of Example 5 is employed as the solidelectrolyte. The electrolyte disc has a diameter of about 0.64 inch. Thecells are discharged at 30K ohm to a cutoff voltage of 1.4 volts. Theaverage performance of the three cells tested is 27 mAh dischargecapacity representing an efficiency of 61% of theoretical input. The MLVis 1.87 volts.

EXAMPLE 12

A microbattery is prepared by depositing the various layers throughappropriate masks. The sputtered layers are deposited using an MRC 903Sputtering System. The microbatteries are constructed under a dry, inertatmosphere (under Ar atmosphere) of below 5 ppm of water. First, achromium layer is deposited by sputtering from a chromium target onto asubstrate through a mask using a DC magnetron sputtering source. A TiS₂target is sputtered through a mask onto the chromium layer and substrateusing a RF magnetron sputtering source. The density of the TiS₂sputtered film is 1.47 g/cm³. The vitreous electrolyte composition isprepared by forming a target of a compressed mixture of 0.20 mole P₂ S₅,0.8 mole Li₃ PO₄ and 1.2 mole LiI. The Li₃ PO₄ is used as both a networkformer and network modifier. A layer of vitreous solid electrolyte isdeposited on the TiS₂ cathode film by sputtering the target using a RFmagnetron sputtering source. A film of LiI is vacuum evaporated onto andcompletely covering the layer of electrolyte. This film forms aprotective layer. Finally, a lithium metal anode layer is vacuumevaporated over a portion of the LiI layer and onto a separate chromiumcontact. The lithium anode is between 1 and 2 microns thick. The totalbattery thickness is about 10 microns. It has an open circuit voltage of2.5 V and exhibits greater than 90% discharge efficiency to a 1.8 Vcutoff for over 5 hours when discharged at 8 microamps/cm². The internalresistance of the battery is about 750 ohms as measured by compleximpedance spectroscopy.

The battery is attached to a dissolved oxygen sensor. The sensorconsists of a silk screened gold working electrode surrounded by achlorided silk screened silver electrode to make a silver/silverchloride counter electrode. A MAX 663 voltage regulator chip from MaximIntegrated Products is used in combination with the battery to supplyand regulate the correct voltage to the sensor electrode. The sensordraws 7-8 microamps from the battery and displays a linear response tooxygen concentration in a solution ranging from 1 to 14 ppm.

What is claimed is:
 1. A precursor mixture corresponding to the formula:

    xLi.sub.2 S, yP.sub.2 S.sub.5, (1-x-y)A, zLiX;

wherein: A is either Li₃ PO₄ or LiPO₃ ; X is a halide; x is a realnumber greater than or equal to 0 and less than or equal to 0.68; y is areal number greater than or equal to 0 and less than or equal to 0.33;x+y is a real number greater than 0 and less than 1; and z is a realnumber greater than or equal to 0.55 and less than or equal to 1.2. 2.The mixture of claim 1, wherein the Lix is selected from the groupconsisting of LiCl, LiBr, LiI, and LiF.
 3. A vitreous solid compositionat 25° C. formed by fusing and cooling the precursor mixture of claim 1.4. The composition of claim 3, wherein the precursor mixture is selectedfrom the group consisting of the formulae:a. 0.66 Li₂ S, 0.26 P₂ S₅,0.08 Li₃ PO₄, 0.57 LiX; b. 0.61 Li₂ S, 0.31 P₂ S₅, 0.08 Li₃ PO₄, 0.62LiX; c. 0.67 Li₂ S, 0.28 P₂ S₅, 0.05 Li₃ PO₄, 0.65 LiX; d. 0.14 Li₂ S,0.23 P₂ S₅, 0.63 Li₃ PO₄, 0.96 LiX; e. 0.25 Li₂ S, 0.25 P₂ S₅, 0.50 Li₃PO₄, 1.0 LiX; f. 0 Li₂ S, 0.20 P₂ S₅, 0.80 Li₃ PO₄, 1.2 LiI; g. 0.61 Li₂S, 0.31 P₂ S₅, 0.08 LiPO₃, 0.62 LiX; h. 0.57 Li₂ S, 0.29 P₂ S₅, 0.14LiPO₃, 0.57 LiX; i. 0.65 Li₂ S, 0.31 P₂ S₅, 0.04 LiPO₃, 0.58 LiX; j.0.50 Li₂ S, 0.17 P₂ S₅, 0.33 LiPO₃, 0.58 LiX.
 5. In an electrochemicalcell employing an active anode material, an active cathode material anda vitreous solid composition at 25° C. as an electrolyte, theimprovement wherein the electrolyte comprises the vitreous solidcomposition of claim
 3. 6. The electrochemical cell of claim 5, whereinthe active anode material is selected from the group consisting oflithium, silver, sodium, potassium and rubidium.
 7. The electrochemicalcell of claim 6, wherein the anode is lithium foil or lithium powder. 8.The electrochemical cell of claim 5, wherein the active cathode materialis selected from TiS₂, FeS₂, Sb₂ S₃, MoS₃, TiS₂ +MoS₃,poly(N-vinylpyrrolidone) (PVP)+iodine, PVP+iodine+TiS₂, organic chargetransfer complexes with halogens, and MnO₂.
 9. The electrochemical cellof claim 8, wherein the active anode material is lithium, and thecathode is a mixture of TiS₂, a conductive agent.
 10. Theelectrochemical cell of claim 9, wherein the anode is lithium foil orlithium powder.
 11. The electrochemical cell of claim 5, wherein Li₂ Sis employed as a network modifier for the vitreous composition.
 12. Theelectrochemical cell of claim 5, wherein P₂ S₅ is employed as a networkformer for the vitreous composition.
 13. The electrochemical cell ofclaim 11, wherein P₂ S₅ is employed as a network former for the vitreouscomposition.
 14. The electrochemical cell of claim 5, wherein the cellis a microbattery having a thickness of less than 100 microns.
 15. Theelectrochemical cell of claim 14, wherein the cell is comprised of asputtered metal film contact supported on a substrate, a sputtered filmcathode layer in contact with the metal film contact, a sputteredelectrolyte layer over the cathode and contact, and a vapor depositedanode layer deposited over the electrolyte layer and a separate metalfilm contact.
 16. The electrochemical cell of claim 15, wherein aprotective layer is deposited over the electrolyte layer, and the anodelayer is vapor deposited in contact with the protective layer.
 17. Theelectrochemical cell of claim 16, wherein the contact is chromium, thecathode is comprised of TiS₂ as the active material, the anode iscomprised of lithium metal as the active material, the protective layeris comprised of LiI, and the electrolyte is formed under glass-formingconditions from a precursor mixture that corresponds to the formula:

    0 Li.sub.2 S, 0.20 P.sub.2 S.sub.5, 0.80 Li.sub.3 PO.sub.4, 1.2 LiI.


18. A device employing the microbattery of claim 16 as a power source.19. A device employing the microbattery of claim 17 as a power source.20. A vitreous composition corresponding to the formula:

    xLi.sub.2 S, yP.sub.2 S.sub.5, (1-x-y)Li.sub.3 PO.sub.4,zLiX;

wherein: X is a halide; x is a real number greater than or equal to 0and less than or equal to 0.68; y is a real number greater than or equalto 0.15 and less than or equal to 0.33; z is a real number greater thanor equal to 0.55 and less than or equal to 1.2; and wherein, either: yis less than 0.2x+0.2, or z is greater than 1.75(1-x+y).
 21. A vitreouscomposition corresponding to the formula:

    xLi.sub.2 S, yP.sub.2 S.sub.5, (1-x-y)LiPO.sub.3, zLiX;

wherein: X is a halide; x is a real number greater than or equal to 0and less than or equal to 0.68; y is a real number greater than or equalto 0.15 and less than or equal to 0.33; z is a real number greater thanor equal to 0.55 and less than or equal to 1.2; and wherein, either: yis less than x-0.33, or z is greater than 1.75(1-x+y).